Wireless communications system, wireless station, base station, and communications method

ABSTRACT

A wireless communications system includes a base station; and a wireless station. The base station, after receiving a first control signal that includes classifying information, configures by a second control signal, transition of a communication mode and releases by a third control signal, the transition of the communication mode. The wireless station performs transition of a mode of communication by the communication mode configured by the second control signal, and releases by the third control signal, the transition of the communication mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication PCT/JP2012/063818, filed on May 29, 2012 and designating theU.S., the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a wirelesscommunications system, a wireless station, a base station, and acommunications method.

BACKGROUND

In wireless communications systems, processing is performed at the radioresource control (RRC) layer and includes the configuration,reconfiguration, and release of connections between wireless stationsand base stations (for example, refer to Japanese Laid-Open PatentPublication No. 2008-199223 and Published Japanese-Translation of PCTApplication, Publication No. 2010-514329). For example, under the 3rdGeneration Partnership Project (3GPP), an RRC connected mode (RRCConnected) and a RRC idle mode (RRC Idle) are specified as states of theRRC layer (for example, refer to 3GPP TS36.331, “Radio Resource Control(RRC) Protocol Specification”, V10.4.0, Release 10, December 2011). TheRRC connected mode, for example, is a state in which data communicationcan be implemented between a wireless station and a base station. TheRRC idle mode, for example, is a state in which data communicationbetween a wireless station and a base station is not possible.

Nonetheless, with the conventional technologies above, even if thecommunication time is short or if a small amount of data is transmitted,overhead for a control signal arises accompanying the transition of thecommunication state and therefore, efficient communication cannot beperformed in some cases.

SUMMARY

According to an aspect of an embodiment, a wireless communicationssystem includes a base station; and a wireless station. The basestation, after receiving a first control signal that includesclassifying information, configures by a second control signal,transition of a communication mode and releases by a third controlsignal, the transition of the communication mode. The wireless stationperforms transition of a mode of communication by the communication modeconfigured by the second control signal, and releases by the thirdcontrol signal, the transition of the communication mode.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sequence diagram depicting one example of operation of awireless communications system according to a first embodiment;

FIG. 2 is a sequence diagram depicting one example of operation of thewireless communications system according to a second embodiment;

FIG. 3 is a diagram depicting one example of a configuration of awireless station;

FIG. 4 is a diagram depicting one example of a configuration of a basestation;

FIG. 5 is a flowchart depicting one example of operation of the wirelessstation according to the second embodiment;

FIG. 6 is a flowchart depicting one example of operation of the basestation according to the second embodiment;

FIG. 7 is a sequence diagram depicting one example of operation ofobtaining UE capability;

FIG. 8 is a sequence diagram depicting one example of operation of thewireless communications system according to a fourth embodiment;

FIG. 9 is a sequence diagram depicting one example of operation oftransmission/reception of a MAC CE;

FIG. 10 is a flowchart depicting one example of operation of thewireless station according to the fourth embodiment;

FIG. 11 is a flowchart depicting one example of operation of the basestation according to the fourth embodiment;

FIG. 12 is a diagram of one example a hardware configuration of thewireless station; and

FIG. 13 is a diagram depicting one example of a hardware configurationof the base station.

DESCRIPTION OF EMBODIMENTS

Embodiments of a wireless communications system, a wireless station, abase station, and a communications method according to the presentinvention will be described in detail with reference to the accompanyingdrawings.

FIG. 1 is a sequence diagram depicting one example of operation of thewireless communications system according to a first embodiment. Thewireless communications system according to the first embodimentincludes a wireless station 101 and a base station 102 depicted inFIG. 1. The base station 102 is, for example, an evolved Node B (eNB) ora Home eNB which deploys a femtocell. The wireless station 101 is, forexample, a mobile station such as a user terminal (User Equipment (UE)).The wireless station 101 and the base station 102 wirelesslycommunication with each other.

The wireless station 101 transmits to the base station 102, a firstcontrol signal that includes classifying information (step S101).Classifying information is information indicating that the wirelessstation 101 is a specific classification (e.g., a static device).

The base station 102 transmits to the wireless station 101, a secondcontrol signal that configures the timing of transition to thecommunication mode (step S102). More specifically, the base station 102determines the timing of transition of the wireless station 101 and thebase station 102 to the first mode. The base station 102 transmits tothe wireless station 101, the second control signal that indicates thedetermined timing of transition. The first mode is a communication modein which data communication is possible, e.g., the connected mode(connected). The timing of transition to the first mode includesmultiple transition timings and for example, is the timing of a constantcycle. The wireless station 101 and the base station 102 respectivelyconfigure therein, the transition timing indicated by the second controlsignal transmitted at step S102 (step S103).

The wireless station 101 and the base station 102 transition to thefirst mode (step S104). The wireless station 101 and the base station102 perform data communication with each other (step S105). The wirelessstation 101 and the base station 102 transition to a second mode (stepS106). The second mode is a non-communication mode in which datacommunication is not possible, e.g., the idle mode (idle).

When the transition timing configured at step S103 arrives, the wirelessstation 101 and the base station 102 transition to the first mode inwhich data communication is possible (step S107). The wireless station101 and the base station 102 perform data communication with each other(step S108). The wireless station 101 and the base station 102transition to the second mode in which data communication is notpossible (step S109). Subsequently, the wireless station 101 and thebase station 102 execute steps S107 to S109, each time the transitiontiming configured at step S103 arrives.

The base station 102 transmits a third control signal to the wirelessstation 101, at an arbitrary timing (step S110). The third controlsignal is a signal instructing release of the transition timingconfigured at step S103. The wireless station 101 and the base station102 release the transition timing configured at step S103 (step S111),ending a series of operations.

Thus, at the predetermined transition timing (step S102, S103), thewireless station 101 and the base station 102 transition to the firstmode, thereby enabling reduction of the control signal overheadaccompanying state transition. For example, at step S107, notificationof the timing of transition to the first mode does not have to be newlygiven to the wireless station 101 from the base station 102, therebyenabling reduction of the control signal overhead accompanying statetransition and facilitating communication efficiency. For example,reduction of the power consumption of the wireless station 101 and thebase station 102 can be facilitated.

The wireless station 101 is, for example, a wireless communicationsapparatus that periodically transmits a small amount of data. In thiscase, if notification of the timing of transition to the first mode isgiven to the wireless station 101 by the base station 102 each time datais transmitted, the control signal overhead for the data to betransmitted becomes large, making efficient communication impossible. Incontrast, at the predetermined transition timing (step S102, S103), thewireless station 101 and the base station 102 transition to the firstmode multiple times, whereby the control signal overhead for the data tobe transmitted becomes relatively smaller, enabling efficientcommunications.

Further, the wireless station 101 and the base station 102 may store awireless parameter used in the data communication at step S105. Awireless parameter is, for example, a parameter that indicates acommunication scheme such as a modulation scheme or coding scheme. Thewireless station 101 and the base station 102 also use the storedwireless parameter in the data communication at step S108. Thus, thewireless station 101 and the base station 102 can communicate data atmultiple timings, by the same wireless parameter. As a result, thecontrol signal overhead accompanying state transition can be reduced.

For example, notification of the wireless parameter used in the datacommunication at step S108 does not have to be given to the wirelessstation 101 by the base station 102, thereby enabling reduction of thecontrol signal overhead accompanying state transition. Further, sincerandom access does not have to be performed for the data communicationat step S108, reduction of the control signal overhead accompanyingstate transition is possible. Therefore, communication efficiency can befacilitated.

The wireless station 101 is, for example, a stationary wirelesscommunications apparatus that is fixed at a given location and performswireless communication. In this case, changes in the wirelessenvironment of the wireless station 101 and the base station 102 aresmall and therefore, even if the wireless parameter is not updated eachtime data is communicated, stable wireless communication can beperformed between the wireless station 101 and the base station 102.

The data communication at steps S105, S108 may be the transmission ofuplink data from the wireless station 101 to the base station 102, orthe transmission of downlink data from the base station 102 to thewireless station 101. Further, the data communication at steps S105,S108 may be both the transmission of uplink data from the wirelessstation 101 to the base station 102 and the transmission of downlinkdata from the base station 102 to the wireless station 101.

Thus, according to the wireless communications system of the firstembodiment, the base station 102, after receiving the first controlsignal that includes classifying information indicating theclassification of the wireless station 101, configures the communicationmode transition timing via the second control signal. Further, theconfigured communication mode transition timing is released by the thirdcontrol signal transmitted by the base station 102. As a result, whenthe wireless station 101 is of a given classification, the controlsignal overhead accompanying state transition is reduced, enablingcommunication efficiency to be facilitated. For example, reduced powerconsumption of the wireless station 101 and the base station 102 can befacilitated.

Here, as one example, a wireless communications system that includes thewireless station 101 and the base station 102 has been described.Nonetheless, architecture of the wireless communications system is notlimited hereto. For example, in the wireless communications systemdepicted in FIG. 1, another example of architecture may be such that arelay station is deployed in place of the wireless station 101.Alternatively, in the wireless communications system depicted in FIG. 1,a relay station may be deployed in place of the base station 102.

Further, although a case has been described where the transition timingof the wireless station 101 and the base station 102 is configured bythe transmission of the second control signal from the base station 102to the wireless station 101, operation is not limited hereto. Forexample, the transition timing of the wireless station 101 and the basestation 102 may be configured by the transmission of the second controlsignal from the wireless station 101 to the base station 102. In thiscase, the transition timing of the wireless station 101 and the basestation 102 is determined by the wireless station 101.

Further, although a case has been described where the configuration ofthe transition timing is released by the transmission of the thirdcontrol signal from the base station 102 to the wireless station 101,operation is not limited hereto. For example, the configuration of thetransition timing may be released by the transmission of the thirdcontrol signal from the wireless station 101 to the base station 102. Inthis case, the timing at which the configured transition timing isreleased is determined by the wireless station 101.

One example of a system to which the wireless communications systemdepicted in FIG. 1 is applied will be described. The wirelesscommunications system depicted in FIG. 1 is, for example, applicable toLong Term Evolution (LTE). Under LTE, a scheme based on orthogonalfrequency division multiplexing (OFDM) is specified as a wireless accesstechnique.

Under LTE, high-speed, wireless packet communication is possible, wherethe peak downlink transmission rate is 100 [Mb/s] or greater, and thepeak uplink transmission rate is 50 [Mb/s] or greater. Aiming to realizeeven faster communication, the 3rd Generation Partnership Project(3GPP), an international standardizing body, has begun investigatingLTE-Advanced (LTE-A) for wireless mobile communications systems, basedon LTE.

The wireless communications system depicted in FIG. 1 can be applied toLTE-A. Under LTE-A, a peak downlink transmission rate of 1 [Gb/s] istargeted, a peak uplink transmission rate of 500 [Mb/s] is targeted, andtechnological investigation of wireless access schemes and networkarchitecture is being conducted.

Under LTE-A (or LTE Rel-11), wireless stations which generate trafficthat differs from the traffic observed in conventional systems areconnected. For example, communication is assumed where various types ofstationary, static devices such as electricity meters including sensorsand gas meters are connected to a cellular network and performcommunication. Such communication is called machine-type communication.

Communication with a fixed timing can be given as one characteristic oftraffic occurring with machine-type communication. For example, anelectricity meter and a gas meter periodically transmit to a server,reports concerning the amount of electricity and gas used. Relativelylow traffic volume is another quality of the traffic occurring withmachine-type communication.

Yet another characteristic of the traffic occurring with machine-typecommunication is that the static devices do not move, eliminating theimportance of system design that considers mobility, which is the pointof mobile communication.

FIG. 2 is a sequence diagram depicting one example of operation of thewireless communications system according to a second embodiment. Thewireless station 101 and the base station 102 of the wirelesscommunications system according to the second embodiment, for example,execute the following steps. During the initial state, the wirelessstation 101 and the base station 102 are both assumed to be in an idlestate.

When data 111 that is to be transmitted to the base station 102 arrives,the wireless station 101 transmits a random access preamble to the basestation 102 (step S201). In response, the base station 102 determinesbased on the reception timing of the random access preamble, thetransmission timing of the uplink signal from the wireless station 101.The determination of the transmission timing of the uplink signal fromthe wireless station 101 can be performed, for example, based on atiming difference of a reception window of the base station 102 and thetiming at which the preamble is received. The base station 102 transmitsto the wireless station 101, a random access response that includesinformation indicating the determined transmission timing (step S202).

Consequent to the random access procedures at steps S201, S202,synchronization is established in the L1 layer (physical layer) and L2layer (media access control layer) of the wireless station 101 and thebase station 102.

The wireless station 101 transmits to the base station 102, a callconnection request (RRC connection request) that includes an identifierof the wireless station 101 and the reason for connection (step S203).Further, the wireless station 101, via the RRC connection request atstep S203, notifies the base station 102 that the wireless station 101is a static device.

Thus, based on the identifier of the wireless station 101 obtained fromthe RRC connection request, the base station 102 identifies the wirelessstation that has come to be connected. In an attempt to setup RRC, thebase station 102 transmits to the wireless station 101, a callconnection setup (RRC connection setup) that includes a wirelessparameter (step S204). The wireless parameter is, for example, aparameter that indicates the communications scheme such as a modulationscheme or a coding scheme. Further, by the RRC connection setup at stepS204, the base station 102 notifies the wireless station 101 of thetiming of transition to the connected mode from the idle mode.

In response, when the configuration of the wireless parameter includedin the RRC connection setup is completed, the wireless station 101transitions to step S205. In other words, the wireless station 101transmits call connection setup complete (RRC connection setup complete)to the base station 102 (step S205). As a result, RRC connection betweenthe wireless station 101 and the base station 102 is established, andthe RRC state of the wireless station 101 and the base station 102transitions to the connected mode from the idle mode.

Next, the base station 102 transmits to the wireless station 101, RRCconnection reconfiguration for configuring reconnection (step S206).Next, the wireless station 101 transmits RRC connection reconfigurationcomplete to the base station 102 (step S207).

The wireless station 101 and the base station 102 execute datacommunication (step S208). For example, at step S208, the data 111arising at step S201 is transmitted from the wireless station 101 to thebase station 102. Subsequently, the wireless station 101 and the basestation 102 transition from the connected mode to the idle mode.

Next, new data 112 that is to be transmitted to the base station 102 isassumed to arrive at the wireless station 101. Thus, the wirelessstation 101 waits until the timing for the transition to the connectedmode, notified at step S204. The wireless station 101 transmits to thebase station 102, a RRC connection re-establishment request that is arequest for reconnection (step S209). Consequently, the wireless station101 and the base station 102 transition to the connected mode from theidle mode.

Next, the base station 102 transmits RRC connection re-establishment tothe wireless station 101 (step S210). The wireless station 101 and thebase station 102 execute data communication (step S211). For example, atstep S211, the data 112 arising at step S209 is transmitted from thewireless station 101 to the base station 102. Subsequently, the wirelessstation 101 and the base station 102 transition to the idle mode fromthe connected mode.

In the case of a transition, a request to re-establish connection isissued to establish security. More specifically, the wireless station101 transmits to the base station 102, a parameter related to security,via an RRC connection re-establishment request. Thus, it is desirablethat the wireless station 101, even while in the idle mode, stores tothe memory, these parameters related to security.

The parameters related to security, for example, include a cell-radionetwork temporary identity (C-RNTI), a short message authentication codefor integrity (short MAC-I), a physical cell identity (PCID), etc.

A short MAC-I is a parameter used for verifying integrity of data(verifying that information is without errors). The short MAC-I, forexample, is included in the RRC connection re-establishment request atstep S209. The base station 102 uses the MAC-I to verify the integrityof RRC connection re-establishment request.

The short MAC-I, for example, is generated by calculating the ID of thecell in which the wireless station 101 is located or the C-RNTI of thewireless station 101 by a security algorithm shared by the wirelessstation 101 and the base station 102. The ID of the cell in which thewireless station 101 is located, for example, includes the ID of thecell in which the wireless station 101 was located before issuing theRRC connection re-establishment request and/or the ID of the cell inwhich the wireless station 101 was located when issuing the RRCconnection re-establishment request.

For the notification that the wireless station 101 is a static device atstep S203, for example, a “delay Tolerant Access-v1020” in the RRCconnection request can be used. Further, for the notification that thewireless station 101 is a static device, a parameter newly specified theRRC connection request may be used. For example, “nm-Access” (non mobileaccess) may be specified in the “spare2” field of the RRC connectionrequest, whereby notification that the wireless station 101 is a staticdevice is given by “nm-Access”.

The timing of transition from the connected mode to the idle mode, forexample, can be the timing when a constant period elapses after thetransition from the idle mode to the connected mode. In this case, thedata communication at steps S208, S211 is completed by the time theconstant period elapses after the transition from the idle mode to theconnected mode.

Alternatively, the timing of transition from the connected mode to theidle mode can be the timing at which data is transmitted/received aftera given period or greater during the connected mode. For example, duringthe connected mode, the wireless station 101 and the base station 102restart a timer at each transmission/reception of data and when thetimer expires, transition to the idle mode. Thus, the period duringwhich the connected mode is maintained can be established according tothe state of communication.

Further, the RRC connection reconfiguration at step S206 may be used inthe notification of the timing of the transition to the connected modefrom the idle mode. When notification of the timing of transition to theconnected mode from the idle mode is given, notification of the timingof transition from the connected mode to the idle mode may also be givento the wireless station 101 by the base station 102.

FIG. 3 is a diagram depicting one example of a configuration of thewireless station. As depicted in FIG. 3, the wireless station 101, forexample, includes a control unit 310, a communications unit 321, and anantenna 322. The communications unit 321, via the antenna 322, performstransmission/reception processing of wirelessly transmitted signals. Thecommunications unit 321, for example, processes radio frequency (RF)signals.

The control unit 310 performs various types of control of the wirelessstation 101. The control unit 310, for example, is a baseband processingunit that processes baseband signals. The control unit 310 includes aPHY control unit 311, a MAC control unit 312, an RRC control unit 313,and a call connection control unit 314.

The PHY control unit 311 processes signals when wireless transmission isperformed. For example, the PHY control unit 311 performs wirelesstransmission according to the modulation and coding of a wireless signalnotified by the base station 102. The MAC control unit 312 performs aprocess related to data scheduling based on wireless resources andtimings instructed by the base station 102.

The RRC control unit 313 controls the operation of the wireless station101. For example, the RRC control unit 313 configures the wirelessresource parameter (e.g., call setup) used for communication, andmanages the communication state of the wireless station 101. Further,the RRC control unit 313 performs a process to transition from the RRCidle mode to the RRC connected mode to enable communication, a handoverprocess to connect to a suitable base station, etc. Further, the RRCcontrol unit 313 performs a process of notifying the base station 102that the wireless station 101 is a static device, via the RRC connectionrequest.

The call connection control unit 314 controls management of the RRCstate by the RRC control unit 313, according to the classification ofthe wireless station 101 and traffic type.

FIG. 4 is a diagram depicting one example of a configuration of the basestation. As depicted in FIG. 4, the base station 102 includes a controlunit 410, a communications unit 421, an antenna 422, and a physical-lineinterface 423. The communications unit 421 transmits and receiveswirelessly transmitted signals, via the antenna 422. Via thephysical-line interface 423, the communications unit 421 furthertransmits and receives signals transmitted by a physical line forcommunication with higher level devices. The communications unit 421,for example, performs transmission/reception processing of RF signals.

The control unit 410 performs various types of control of the basestation 10. The control unit 410, for example, is a baseband processingunit that processes baseband signals. The control unit 410 includes aPHY control unit 411, a MAC control unit 412, an RRC control unit 413,and a call connection control unit 414.

The PHY control unit 411 processes signals when wireless transmission isperformed. For example, the PHY control unit 411 determines themodulation and coding scheme of wireless signals. The MAC control unit412 performs a process related to data scheduling.

The RRC control unit 413 controls the operation of the base station 102.For example, the RRC control unit 413 configures the wireless resourceparameter (e.g., call setup) used for communication, and manages thecommunication state of the base station 102. For example, the RRCcontrol unit 413 performs a process to transition from the idle mode tothe connected mode to enable communication, and a handover process forconnection to a suitable base station. Further, the RRC control unit 413obtains, by RRC connection request, information indicating that thewireless station 101 is a static device.

The call connection control unit 414 identifies the classification ofthe wireless station 101 and traffic type, and controls the managementof the RRC state, based on the identification results.

(Operation of Wireless Station)

FIG. 5 is a flowchart depicting one example of operation of the wirelessstation according to the second embodiment. The wireless station 101,for example, executes the following steps. The wireless station 101performs call setup with the base station 102 (step S501). The callsetup at step S501, for example, corresponds to the operations at stepsS201 to S205 depicted in the FIG. 2. Further, the wireless station 101,via the RRC connection request in the call setup at step S501, notifiesthe base station 102 that the wireless station 101 is a static device.

The wireless station 101 receives from the base station 102,configuration information for an RRC transition pattern (step S502). AnRRC transition pattern is, for example, the transition timing of the RRCstate. The wireless station 101 stores to the memory, the configurationinformation received at the step S502, for the RRC transition pattern(step S503).

The wireless station 101 judges based on the configuration informationstored at step S503, whether the current time is the transition timingfor transitioning to the connected mode (step S504). If the current timeis not the transition timing for transitioning to the connected mode(step S504: NO), the wireless station 101 proceeds to step S507.

At step S504, if the current time is the transition timing fortransitioning to the connected mode (step S504: YES), the wirelessstation 101 transitions to the connected mode and executes datacommunication with the base station 102 (step S505). The datacommunication at step S505, for example, includes the scheduling of datacommunication by the MAC control unit 312, the transmission or receptionof radio waves by the PHY control unit 311, etc.

The wireless station 101 judges based on the configuration informationstored at step S503, whether the current time is the transition timingfor transitioning to the idle mode (step S506). If the current time isnot the transition timing for transitioning to the idle mode (step S506:NO), the wireless station 101 returns to step S505, and continuesperform the data communication.

At step S506, if the current time is the transition timing fortransitioning to the idle mode (step S506: YES), the wireless station101 transitions to the idle mode (step S507). Here, the wireless station101 retains the wireless parameter configured in the call setup at stepS501, and uses the same wireless parameter in the next transition to theconnected mode. At step S507, if the wireless station 101 is already inthe idle mode, the wireless station 101 maintains the idle mode.

The wireless station 101 judges whether to release (detach) a non-accessstratum (NAS) connection (step S508). If the NAS connection is not to bereleased (step S508: NO), the wireless station 101 returns to step S504.If the NAS connection is to be released (step S508: YES), the wirelessstation 101 ends a series of operations.

FIG. 6 is a flowchart depicting one example of operation of the basestation according to the second embodiment. The base station 102, forexample, executes the following steps. The base station 102 performscall setup with the wireless station 101 (step S601). The call setup atstep S601, for example, corresponds to the operations at steps S201 toS205 depicted in FIG. 2. Further, the base station 102, via the RRCconnection request in the call setup at step S601, obtains from thewireless station 101, information indicating whether the wirelessstation 101 is a static device.

The base station 102 judges based on the information obtained in thecall setup at step S601, whether the wireless station 101 is a staticdevice (step S602). If the wireless station 101 is a static device (stepS602: YES), the base station 102 transmits to the wireless station 101,configuration information for the RRC transition pattern (step S603).The RRC transition pattern is, for example, the transition timing of theRRC state. Next, the base station 102 stores to the memory, theconfiguration information transmitted at the step S603, for RRCtransition pattern (step S604).

The base station 102 judges based on the configuration informationstored at step S604, whether the current time is the transition timingfor transitioning to the connected mode (step S605). If the current timeis not the transition timing for transitioning to the connected mode(step S605: NO), the base station 102 proceeds to step S608.

At step S605, if the current time is the transition timing fortransitioning to the connected mode (step S605: YES), the base station102 judges that the wireless station 101 has transitioned to theconnected mode and executes data communication with the wireless station101 (step S606). The data communication at step S606, for example,includes the scheduling of data communication by the MAC control unit412, and the transmission or the reception of radio waves by the PHYcontrol unit 411.

The base station 102 judges based on the configuration informationstored at step S604, whether the current time is the transition timingfor the wireless station 101 to transition to the idle mode (step S607).If the current time is not the transition timing for the wirelessstation 101 to transition to the idle mode (step S607: NO), the basestation 102 returns to step S606 and continues to perform the datacommunication.

At step S607, if the current time is the transition timing fortransitioning to the idle mode (step S607: YES), the base station 102judges that the wireless station 101 has transitioned to the idle mode(step S608). Here, the base station 102 retains the wireless parameterconfigured in the call setup at step S601, and uses the same wirelessparameter in the next transition to the connected mode. At step S608, ifthe wireless station 101 is already in the idle mode, the base station102 maintains the idle mode.

The base station 102 judges whether to release (detach) the NASconnection (step S609). If the NAS connection is not to be released(step S609: NO), the base station 102 returns to step S605. If the NASconnection is to be released (step S609: YES), the base station 102 endsa series of operations.

At step S602, if the wireless station 101 is not a static device (stepS602: NO), the base station 102 judges whether the wireless station 101transitions to the connected mode (step S610). At step S610, judgment ofwhether to transition to the connected mode can be performed, forexample, based on whether there is a connection request from thewireless station 101. If the wireless station 101 is judged not totransition to the connected mode (step S610: NO), the base station 102proceeds to step S614.

At step S610, if the wireless station 101 is judged to transition to theconnected mode (step S610: YES), the base station 102 judges that thewireless station 101 has transitioned to the connected mode, andexecutes data communication with the wireless station 101 (step S611).The data communication at step S610, for example, includes thescheduling of data communication by the MAC control unit 412, thetransmission or reception of radio waves by the PHY control unit 411,etc.

The base station 102 judges whether the wireless station 101 transitionsto the idle mode (step S612). If the wireless station 101 is judged tonot transition to the idle mode (step S612: NO), the base station 102returns to step S611 and continues to perform the data communication.

At step S612, if the wireless station 101 is judged to transition to theidle mode (step S612: YES), the base station 102 transmits to thewireless station 101, an RRC connection release, and the wirelessstation 101 transitions to the idle mode (step S613).

The base station 102 judges whether to release the NAS connection (stepS614). If the NAS connection is not to be released (step S614: NO), thebase station 102 returns to step S610. If the NAS connection is to bereleased (step S614: YES), the base station 102 transmits to thewireless station 101, a control signal instructing the release of theNAS connection, and ends a series of operations.

In this manner, according to the wireless communications system of thesecond embodiment, the base station 102 receives from the wirelessstation 101, a RRC connection request (first control signal) thatincludes classifying information indicating that the wireless station101 is a static device (specific classification). In this case, the basestation 102 configures, via RRC connection setup or RRC connectionreconfiguration (second control signal), the transition timing fortransitioning to the connected mode (communication mode). Further, thetransition to the configured communication mode is released by a controlsignal (third control signal) instructing the release of the NASconnection. As a result, if the wireless station 101 is not a staticdevice, the RRC control signal overhead accompanying state transition isreduced, enabling communication efficiency to be facilitated.

In the wireless communications system according to a third embodiment,portions differing from the wireless communications system according tothe second embodiment will be described.

The wireless station 101 according to the third embodiment notifies thebase station 102 that the wireless station 101 is a static device, viaUE capability. UE capability is, for example, specified under LTERel-10, and is information that notifies the base station 102, to whichcategory the wireless station 101 belongs. As a result, the wirelessstation 101 can notify the base station 102 of the communicationperformance of the wireless station 101.

For example, a category, “Category 9” can be newly configured for astatic device, and the value of the data size can be configured to besmaller (e.g., ⅛) than that of “Category 1”. The wireless station 101transmits to the base station 102, the UE capability, which indicates“Category 9”. As a result, the base station 102 can judge that thewireless station 101 is a static device having a communication data sizethat is small.

FIG. 7 is a sequence diagram depicting one example of operation ofobtaining the UE capability. The wireless station 101 and the basestation 102, for example, execute the following steps at the time ofcall setup, for example. The base station 102 transmits to the wirelessstation 101, a UE capability enquiry requesting the UE capability (stepS701).

The wireless station 101 transmits to the base station 102, UEcapability enquiry information that includes “Category 9” (step S702).As a result, the base station 102 obtains the UE capability indicating“Category 9”, and the base station 102 can judge that the wirelessstation 101 is a static device.

In this manner, according to the wireless communications system of thethird embodiment, the wireless station 101 can notify the base station102, that the wireless station 101 is a static device, via the UEcapability.

In the wireless communications system according a fourth embodiment,portions differing from the wireless communications system according tothe second embodiment or the third embodiment will be described.

Even if the wireless station 101 is a static device, the static devicemay not always be static such as in the case of a health meter orsecurity sensor. Thus, the base station 102 transmits activation signals(Activation) and deactivation signals (Deactivation) to the wirelessstation 101. Activation is a signal instructing transition to a mode ofperforming state transition by a preconfigured timing. Deactivation is athird control signal instructing transition to a mode of configuring thetransition timing for each data communication and performing statetransition.

For example, even if the wireless station 101 is not a static device and“Category 9” is set in the category of the UE capability, the basestation 102 can judge that the volume of data transmitted from thewireless station 101 is small. In this case, by transmitting Activationto the wireless station 101, the base station 102 can transition to themode of performing state transition by a preconfigured timing, even ifthe wireless station 101 is not a static device.

Further, although the base station 102 performs communication by a modeof performing state transition by a preconfigured timing, if a mode ofconfiguring the transition timing at each data communication andperforming state transition is transitioned to, Deactivation istransmitted to the wireless station 101.

The transmission of Activation or Deactivation from the base station102, for example, can be performed by the transmission of a physicaldownlink control channel (PDCCH) by the PHY control unit 411 or the MACcontrol unit 412. The reception of Activation or Deactivation by thewireless station 101, for example, can be performed by the reception ofthe PDCCH by the PHY control unit 311 or the MAC control unit 312.

FIG. 8 is a sequence diagram depicting one example of operation of thewireless communications system according to the fourth embodiment. Thewireless station 101 and the base station 102 of the wirelesscommunications system according to the fourth embodiment, for example,execute the following steps. In the initial state, the wireless station101 and the base station 102 are respectively in the idle mode (Idle).

Steps S801 to S805 depicted in FIG. 8 are identical to steps S201 toS205 depicted in FIG. 2. After step S805, the base station 102 transmitsActivation to the wireless station 101 (step S806). As a result, thewireless station 101 and the base station 102 transition to the mode ofperforming state transition by a preconfigured timing.

Steps S807 to S812 depicted in FIG. 8 are identical to steps S206 toS211 depicted in FIG. 2. After step S812, the base station 102 transmitsDeactivation to the wireless station 101 (step S813). As a result, themode of performing state transition by a preconfigured timing isreleased, and the wireless station 101 and the base station 102transition to the mode of configuring the transition timing at each datacommunication and performing state transition.

A PDCCH can be used at the control signal giving notification ofActivation and Deactivation, for example. Alternatively, a MAC controlelement (CE) can be used as the control signal giving notification ofActivation and Deactivation.

FIG. 9 is a sequence diagram depicting one example of operation oftransmission/reception of a MAC CE. When a MAC CE is used as the controlsignal giving notification of Activation and Deactivation, the wirelessstation 101 and the base station 102, for example, execute the followingsteps.

If the wireless station 101 is not a static device and “Category 9” isset in the category of the UE capability, the base station 102 transmitsto the wireless station 101, a MAC CE giving notification of Activation(step S901). The wireless station 101 transmits to the base station 102,an ACK, which is a response signal for the MAC CE transmitted at stepS901 (step S902). As a result, the wireless station 101 and the basestation 102 transition to the mode of performing state transition by apreconfigured timing.

Further, if the mode of performing state transition by a preconfiguredtiming is to be terminated, the base station 102 transmits to thewireless station 101, a MAC CE giving notification of Deactivation (stepS903). The wireless station 101 transmits to the base station 102, anACK, which is a response signal for the MAC CE transmitted at step S903(step S904). As a result, the wireless station 101 and the base station102 transition to the mode of configuring the transition timing at eachdata communication and performing state transition.

FIG. 10 is a flowchart depicting one example of operation of thewireless station according to the fourth embodiment. If the wirelessstation 101 is static device, the wireless station 101 according to thefourth embodiment, for example, executes the steps depicted in FIG. 5.If the wireless station 101 is not a static device, the wireless station101 according to the fourth embodiment, for example, executes thefollowing steps. Steps S1001 to S1003 depicted in FIG. 10 are identicalto steps S501 to S503 depicted in FIG. 5. However, at step S1001, thewireless station 101 does not notify the base station 102 that thewireless station 101 is a static device.

After step S1003, the wireless station 101 judges whether Activation viaa PDCCH has been received from the base station 102 (step S1004). IfActivation has not been received (step S1004: NO), the wireless station101 ends a series of operations. If Activation has been received (stepS1004: YES), the wireless station 101 proceeds to step S1005. StepsS1005 to S1007 depicted in FIG. 10 are identical to steps S504 to S506depicted in FIG. 5.

At step S1007, if the transition timing for transitioning to the idlemode has arrived (step S1007: YES), the wireless station 101 judgeswhether Deactivation via a PDCCH has been received from the base station102 (step S1008). If Deactivation has not been received (step S1008:NO), the wireless station 101 returns to step S1005. As a result, thewireless station 101 retains the wireless parameter configured in thecall setup at step S1001, and uses the same wireless parameter for thenext transition to the connected mode. If Deactivation has been received(step S1008: YES), the wireless station 101 ends a series of operations.

FIG. 11 is a flowchart depicting one example of operation of the basestation according to the fourth embodiment. The base station 102according to the fourth embodiment, for example, executes the followingsteps. The base station 102 performs call setup with the wirelessstation 101 (step S1101). The call setup at step S1101, for example,corresponds to the operations at steps S201 to S205 depicted in FIG. 2.Further, via the RRC connection request in the call setup at step S1101,the base station 102 obtains from the wireless station 101, informationindicating whether the wireless station 101 is a static device.

The base station 102 transmits preconfiguration information of a RRCtransition pattern to the wireless station 101 (step S1102). The RRCtransition pattern is, for example, the transition timing of the RRCstate. The base station 102 stores to the memory, the configurationinformation of the RRC transition pattern, transmitted at step S1102(step S1103). The base station 102 judges based on the informationobtained at step S1101, whether the wireless station 101 is a staticdevice (step S1104). If the wireless station 101 is a static device(step S1104: YES), the base station 102 proceeds to step S1105. StepsS1105 to S1107 are identical to steps S605 to S607 depicted in FIG. 6.

At step S1107, if the transition timing for transitioning to the idlemode has arrived (step S1007: YES), the base station 102 judges whetherto transmit Deactivation (step S1108). Judgment of whether to transmitDeactivation to the wireless station 101, for example, can be performedbased on a state such as the moving state of the wireless station 101.For example, if the base station 102 obtains from the wireless station101, information indicating the traveling speed of the wireless station101 and the traveling speed of the wireless station 101 exceeds athreshold, the wireless station 101 is judged to be moving andDeactivation is transmitted.

At step S1108, if Deactivation is not to be transmitted (step S1108:NO), the base station 102 returns to step S1105. Here, the base station102 retains the wireless parameter configured in the call setup at stepS1101 and uses the same wireless parameter for the next transition tothe connected mode. If Deactivation is to be transmitted (step S1108:YES), the base station 102 transmits Deactivation to the wirelessstation 101, via a PDCCH (step S1109), ending a series of operations.

At step S1104, if the wireless station 101 is not a static device (stepS1104: NO), the base station 102 judges whether to transmit Activationto the wireless station 101 (step S1110). The judgment of whether totransmit Activation to the wireless station 101, for example, can beperformed based on a state such as the moving state of the wirelessstation 101. For example, if the base station 102 obtains from thewireless station 101, information indicating the traveling speed of thewireless station 101 and the traveling speed of the wireless station 101is less than or equal to a threshold for a given period or long, thewireless station 101 judges that the wireless station 101 is not movingand transmits Activation.

At step S1110, if Activation is not to be transmitted (step S1110: NO),the base station 102 proceeds to step S1112. Steps S1112 to S1116depicted in FIG. 11 are identical to steps S610 to S614 depicted in FIG.6. If Activation is to be transmitted (step S1110: YES), the basestation 102 transmits Activation to the wireless station 101, via aPDCCH (step S1111), and proceeds to step S1105.

In this manner, according to the wireless communications system of thefourth embodiment, when the wireless station 101 is not a static device(the specific classification of a wireless station), the method oftransitioning states can be switched according to the state (e.g.,moving state) of the wireless station 101. More specifically, a state ofperforming communication mode transition based on the configuration ofthe second control signal and a state of performing communication modetransition irrespective of the configuration of the second controlsignal can be switched between, according to the state of the wirelessstation 101.

As a result, if the wireless station 101 is a static device, a mode ofstate transition can be switched between a mode in which the statetransition is performed by a predetermined configuration timing and amode in which the state transition is performed by configuring thetransition timing at each data communication, according to the state ofthe wireless station 101. For example, if the wireless station 101 isnot moving, by configuring the mode of performing state transition by apredetermined configuration timing, communication efficiency can befacilitated. Further, if the wireless station 101 is moving, byconfiguring the mode of performing state transition by configuration ateach data communication, improved communication quality can befacilitated.

FIG. 12 is a diagram of one example a hardware configuration of thewireless station. The wireless station 101 of each of the embodimentsdescribed above, for example, can be implemented by a communicationsapparatus 1200 depicted in FIG. 12. The communications apparatus 1200includes a display unit 1201, an input unit 1102, a communicationsinterface 1203, an antenna 1204, a wireless communications unit 1205,read-only memory (ROM) 1206, a processor 1207, a main memory 1208, and abus 1220.

The display unit 1201, the input unit 1102, the communications interface1203, the wireless communications unit 1205, the ROM 1206, and the mainmemory 1208 are connected, via the bus 1220, to the processor 1207.

The display unit 1201 is a user interface that displays information forthe operator. The display unit 1201, for example, is a liquid crystaldisplay. The input unit 1102 is a user interface that receives input ofinformation from the operator. The input unit 1102, for example, is akeypad or the like. The operator of the communications apparatus 1200operates the communications apparatus 1200 by using the display unit1201 and the input unit 1102, such as to input a telephone number.

The communications interface 1203, for example, is a speaker and amicrophone. The operator of the communications apparatus 1200 uses thecommunications interface 1203 for audio telephone calls.

The antenna 1204 is connected to the wireless communications unit 1205.The wireless communications unit 1205 performs wireless communicationvia the antenna 1204 and under the control of the processor 1207.

The ROM 1206, for example, stores programs for executing various typesof processes. The processor 1207 reads out various types of programsstored on the ROM 1206, loads the read program onto the main memory1208, and executes various types of processes. A central processing unit(CPU), a field programmable gate array (FPGA), and the like may be usedas the processor 1207, for example.

The antenna 322 depicted in FIG. 3, for example, may be implemented bythe antenna 1204. The communications unit 321 depicted in FIG. 3, forexample, may be implemented by the processor 1207 and the wirelesscommunications unit 1205. The control unit 310 depicted in FIG. 3, forexample, may be implemented by the ROM 1206, the processor 1207, and themain memory 1208.

FIG. 13 is a diagram depicting one example of a hardware configurationof the base station. The base station 102 according the embodimentsdescribed above, for example, may be implemented by a communicationsapparatus 1300 depicted in FIG. 13. The communications apparatus 1300includes a display unit 1301, an input unit 1302, a communicationsinterface 1303, an antenna 1304, a wireless communications unit 1305,ROM 1306, a processor 1307, main memory 1308, storage 1309, and a bus1320.

The display unit 1301, the input unit 1302, the communications interface1303, the wireless communications unit 1305, the ROM 1306, the mainmemory 1308, and the storage 1309 are connected, via the bus 1320, tothe processor 1307.

The display unit 1301 is a user interface that displays information forthe operator. The display unit 1301, for example, is a monitor. Theinput unit 1302 is a user interface that receives the input ofinformation from the operator. The input unit 1302, for example, is akeyboard. The operator of the communications apparatus 1300 operates thecommunications apparatus 1300 by using the display unit 1301 and theinput unit 1302, such as for inputting information for a setup program.

The communications interface 1303, for example, is a communicationsinterface for communicating with higher level stations. Thecommunications interface 1303, for example, is a network interface, ananalog/digital converter (ADC), etc.

The antenna 1304 is connected to the wireless communications unit 1305.The wireless communications unit 1305 performs wireless communication,via the antenna 1304 and under the control of the processor 1307.

The ROM 1306, for example, stores programs for executing various typesof processes. The processor 1307 reads out various types of programsstored on the ROM 1306, loads the read program onto the main memory1308, and executes various types processes. A CPU, FPGA, and the likemay be used as the processor 1307, for example. The storage 1309, forexample, is a storage apparatus such as a hard disk. For example, afunction of a buffer is implemented by the storage 1309 and theprocessor 1307.

The antenna 422 depicted in FIG. 4, for example, may be implemented bythe antenna 1304. The physical-line interface 423 depicted in FIG. 4,for example, may be implemented by the communications interface 1303.The communications unit 421 depicted in FIG. 4, for example, may beimplemented by the processor 1307 and the wireless communications unit1305. The control unit 410 depicted in FIG. 4, for example, may beimplemented by the ROM 1306, the processor 1307, and the main memory1308.

As described, the wireless communications system, the wireless station,the base station, and the communications method enable communicationefficiency to be facilitated.

In the mode of performing state transition by a preconfigured timing,the wireless station 101, which is a static device, does not move andtherefore, although deviation of uplink synchronization is low, thetiming of uplink transmission may deviate gradually consequent to theprecision of the clock of the static device. Therefore, operation may besuch that when a given period has elapsed since the time when theconnected mode is entered, the wireless station 101 and the base station102 again implement the random access procedure.

According to one aspect of the present invention, communicationefficiency can be facilitated.

All examples and conditional language provided herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventor to further the art, and arenot to be construed as limitations to such specifically recited examplesand conditions, nor does the organization of such examples in thespecification relate to a showing of the superiority and inferiority ofthe invention. Although one or more embodiments of the present inventionhave been described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A wireless communications system comprising: abase station; and a wireless station, wherein the base station, afterreceiving a first control signal that includes classifying information,configures by a second control signal, transition of a communicationmode and releases by a third control signal, the transition of thecommunication mode, and the wireless station performs transition of amode of communication by the communication mode configured by the secondcontrol signal, and releases by the third control signal, the transitionof the communication mode.
 2. The wireless communications systemaccording to claim 1, wherein the first control signal is a signal thatis transmitted from the wireless station and indicates that the wirelessstation is a wireless station of a specific classification.
 3. Thewireless communications system according to claim 1, wherein the secondcontrol signal is a signal that is transmitted from the base station tothe wireless station and indicates a plurality of timings for the basestation and the wireless station to transition to adata-communication-enabled mode, and the base station and the wirelessstation transition to the data-communication-enabled mode, at theplurality of timings indicated by the second control signal.
 4. Thewireless communications system according to claim 3, wherein the basestation and the wireless station perform the data communication at theplurality of timings, by a same wireless parameter.
 5. The wirelesscommunications system according to claim 3, wherein the plurality oftimings is a timing of a constant cycle, and the wireless stationperiodically transmits data to the base station.
 6. The wirelesscommunications system according to claim 2, wherein a state ofperforming the transition of the communication mode based on aconfiguration of the second control signal and a state of performing thetransition of the communication mode irrespective of the configurationof the second control signal are switched between, according to a stateof the wireless station and when the wireless station is not a wirelessstation of the specific classification.
 7. A wireless station thatperforms wireless communication by preconfiguring transition of acommunication mode, the wireless station comprising: a processorconfigured to: transmit to a base station, a first control signal thatincludes classifying information; receives from the base station, asecond control signal that configures the transition of thecommunication mode; and receives from the base station, a third controlsignal that releases the transition of the communication mode; andperforms control such that, after the second control signal is received,performs wireless communication by making the mode transition to thepreconfigured communication mode.
 8. A base station that performswireless communication by preconfiguring a transition of a communicationmode, the base station comprising: a processor configured to: receivefrom a wireless station, a first control signal that includesclassifying information; transmit to the wireless station, a secondcontrol signal that configures the transition of the communication mode;transmit to the wireless station, a third control signal that releasesthe transition of the communication mode; and perform control such thatafter the second control signal is transmitted, perform wirelesscommunication by making the mode transition to the preconfiguredcommunication mode.